1. Field of the Invention
This invention relates to an empirically verified method to objectively quantitate the blurriness of ocular fundus images. More specifically, the invention relates to a comparison of multiple methods of image analysis as tested against a standard subjective grading system in order to permit automated grading of the severity of vitritis.
2. Brief Description of the Related Art
Intraocular inflammatory processes lead to progressive accumulation of cells and protein exudate in the vitreous, often referred to as vitreous haze. Vitreous haze serves as a surrogate marker for intraocular inflammation caused by variety of inflammatory diseases known as uveitis. It has been used currently as a primary outcome for clinical trials in uveitis. The amount of vitreous haze can change over the course of the disease and it is expected to decrease or disappear when adequately treated with anti-inflammatory medications. Vitreous haze can be detected by ophthalmoloscopic inspection of the eye as decreased visibility of the retinal vasculature, optic nerve head, and other fundus details. Several photographic scales are currently used in an attempt to standardize clinical grading of vitreous haze. The estimation of the amount of the haze is subjective and changes in condition can be difficult to identify and report because the range of grades is sparse and skewed due to poor discriminability at low levels of haze. In order to standardize the grading of the vitreous haze a clinical photographic scale has been proposed. Recently, a new digital photographic scale comprising of fundus photographs with increasing amount of blur has been introduced by J. Davis, B Madow et. al. (Am. J. Ophthalmology, 2010, 2011). It has been successfully used in the reading center environment to more precisely judge vitreous opacification where the photograph with unknown amount of vitreous haze is judged against a set of standard photos with known amounts of haze. However, since it is subjective, often there is disagreement between multiple graders as to the exact value of the grade. In addition, it takes significant amount of time to perform the grading.
What is needed is a method for grading the blurring of ocular fundus images to permit automated objective grading of severity of vitritis in a more efficient manner. However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the field of this invention how the shortcomings of the prior art could be overcome.